Thermal operator



July 20-, 1943. I w. A RAY THERMAL OPERATOR Filed May 3, 1941 Bnventor,

1900M mamas r4 MAL/AM ,4. PA

attorneg Patented July 20, 1943 OFFICE THERMAL OPERATOR William A. Ray, Glendale, Calif.

' Application May 3, 1941, Serial No. 391,757

5 Claims.

My present invention relates to electrically energized heat motors of the type wherein the force produced by thermal expansion of a volatile fluid is employed to move a wall, forming a part of a closed system, for the operation of a control device such as a fluid control valve, damper, or the like.

An object of my invention is to provide means for'so improving the operation of such a motor that its rate of movement, both upon energization and deenergization, is increased.

Another object of my invention is to provide, in a heat motor of the type indicated, means for so controlling the electrical energy supplied to the heating element thereof that upon energization high fluid pressure is rapidly produced, the means also acting to prevent subsequent overheating of the fluid so that upon deenergization the reduction of fluid pressure is also rapid.

Another object is to provide means, responsive both to the temperature of fluid in the system and also to the heat radiated from the electrical heating element, for controlling the energization of the same.

Another object is to provide a two-part elec-. trical heating unit, one part of which is constantly energized during the pressure-producing cycle of the motor, the other part of the heating unit being so thermostatically controlled that it is energized generally only upon initiation of the pressure-producing cycle, and also intermittently to .compensate for heat losses during prolonged operation.

Other objects and advantages of my invention will be found in the description, the drawing. and the appended claims.

For complete understanding of the invention, reference may be had t the following detailed description and accomp nying drawing, the single'flgure of which isa view, partly in diagram, of a heat motor control' system embodying my invention.

In the drawing, the numeral ll indicates a cylindrical bulb constructed of metal, such as copper, having good heat conductivity. Connected to the lower end of bulb II by a pipe I2 is a motor generally indicated by the numeral l3 and comprising a cylindrical casing l4, to the flanged bottom end ofwhich is secured, as by a plate IS, the marginal bottom end portion of an expansible-contractible bellows member IS. The upper end of the bellows is secured by plates i1 and nut IE to an operating stem l9 which extends downwardly through a central opening in plate l5 and carries at its bottom a closure mem- Ill) wardly biased by a spring 22, compressed-be tween plates l5 and i1, so that the closure member is normally held in engagement with its seat 23. The system, including the interior of bulb II and the space-between bellows i6 and easing I4, is charged with a volatile liquid such as acetone or ethyl alcohol.

For the heating of bulb II a resistance coil 24 is provided which is wound around a substantial portion of the bulb and is electrically insulated therefrom by an interposed wrapping 25 of material such as mica. Intimately secured by rivets 26 to the head 2? of bulb l l which head is preferably of the same metal as the bulb, is a bimetallic member 28. The free end of the bimetallic member extends outwardly and downwardly adjacent the upper portion of the coil 24 and carries at its extremity a contact element 29 which is cooperable with a relatively fixed contact element 30. Terminals 3i and 32 are provided for the connection to the system of an external source of electrical energy; terminal 32" being connected by a wire 33 directly to the lower end of coil 24, and terminal 3| being connected by wire 34, through a thermostat 35, to an intermediate portion of the coil. The upper end of coil 24 is connected by a wire 36 to the headed-over rear portion of contact 29, the fixed contact being connected by a wire 31 to the supply wire 33. It will thus be seen that, when the switching means of thermostat are closed, current can flow through the lower portion of the heating coil and, when the contacts 29 and 30 are in engagement, current also can flow in parallel to the upper portion of the heating coil.

Assuming that the valve 2| is connected to supply fuelto a device for heating the space wherein thermostat 35 is located, when, in response to demand for heat the thermostat closes the circuit to the source of electrical energy, current will flow, as described above, to both upper and lower portions of coil 24, it being assumed that bulb l l is cold and that the bimetallic member 28 connected thereto is so constructed and arranged that when cold it is warped into contact-closing position. The bulb is thus rapidly heated and the thermal expansion of the fluid,

therein, applied to bellows I6; acts to force the same downward, opening the closure member of valve 2| so that fuel is supplied to the spaceheating device. Assuming" that the temperature of the space is relatively-low and that the thermostat therefore remains closed for a considerable length of time, after a short interval the bimetallic member 28 will be so heated by conduction from bulb l I and also by radiation from the upper portion of the heating coil that it will warp to contact-opening position, in engagement with stop 38. So as to minimize arcing at contacts 29 and 30 in the movement of the bimetallic member, snap action is provided by a spring 39 compressed against the end of the member. Energy is thus now supplied only to the lower portion of the heating coil, the heat of which is normally sufilcient to maintain the pressure of the fluid inthe system such that valve 2| remains open. If however, thermostat 35 remaining closed, the heat losses in the system are such that the temperature of bulb II is substantially reduced, the bimetallic member 28 warps to contact-closing position, with the result that the upper portion of the heating coil is again momentarily energized. It will thus be seen that the pressure of the fluid in the system is maintained at a degree just sufficient to hold the fuel supply valve in open position, so that the closing of the same is rapid when thermostat 35 eventually opens.

By making the bimetallic member 28 responsive to both the temperature of bulb II and also, in some degree, to the heat-radiated by the upper portion of the coil, overrun due to the thermal lag of this portion'of the coil is avoided. By subjecting a portion of a bimetallic member to radiation from the heating coil, a form of heat-anticipation" is effected which is analogous to that produced by the additional heating unit provided in some room thermostats for preventing the effect of the thermal lag of the spaceheating device. In other words, by thus positioning the bimetallic member, contacts 29 and 30 will be opened when the temperature at the top of the bulb is below that which, after these contacts open, it will later reach due to the thermal lag of the upper portion of the heating coil.

It will be appreciated that heat is also con ducted by convection from the heating coil to the bimetallic member. It also will be understood that the major thermal eifect on the bimetallic member is due to conduction of heat from the fluid in the bulb, and that radiation from the coil has but an auxiliary effect. Due to the high 'thermal conductivity of the metal of which the bulb is constructed, the temperature of the'bulb is substantially the' same as that of the fluid therein.

While I have herein shown and described a specific embodiment of my invention, I wish it to be understood that modifications may 'be made without departing from the spirit of the invention and that I intend therefore to be limited only by the scope of the appended claims.

This application is a continuation in part of my copending application Serial No. 175,468, filed November 19, 1937, now abandoned.

I claim as my invention:

1. In a heat motor: a first vessel having a movable wall, a. second vessel in communication with said first vessel and forming therewith a closed system, a volatile fluid in said system, said second vessel being of elongated form and constructed of metal having good heat conductivity, an electrical heating coil surrounding one portion of said second vessel, a bimetallic member mounted on another portion of said second vessel and in good heat-conducting relation thereto, said bimetallic member being spaced closely adjacent a portion of said heating coil so that it is affected to a minor degree also by heat radiated therefrom, and switching means actuated by said bimetallic member for controlling the energization of said heating coil, the effect of said radiated heat upon said bimetallic member being to cause deenergization of the heating coil by said switching means when the temperature of the second vessel is below that Which it subsequently reaches due to the thermal lag of the heating coil.

2. In a heat motor: a first vessel having a mov able wall, a second vessel in communication with said first vessel and forming therewith a closed system, a volatile fluid in said system, saidsecond vessel being of elongated form and constructed of metal having good heat conductivity, said second vessel being so mounted that its major axis is substantially vertical, an electrical heating coil surrounding a portion of the side wall of said second vessel, a bimetallic member mounted by one of its end portions on th top wall of said second vessel and in good heat-conducting relation thereto, the other end portion of the bimetallic member extending generally laterally closely adjacent the upper portion of said coil so that it is also affected to a minor degree by heat radiated therefrom, and switching means actuated by the movement of said bimetallic member for controlling the energization of said heating coil, the efiect of said radiated heat upon said bimetallic member being to cause deenergization of said heating coil by said switching means when the temperature of the second vessel is below that which it subsequently reaches due to the thermal lag of the heating coil.

3. In a heat motor: a first vessel having a movable wall, a second vessel in communication with said first vessel and formin therewith a closed system, a volatile fluid in said system, said second vessel being of elongated form and constructed of metal having good heat conductivity, a first electrical heating coil surrounding one portion of said second vessel, a second electrical heating coil surrounding another portion of said second vessel, a bimetallic member mounted on still another portion of said second vessel and in good heat-conductin relation thereto, said' bimetallic member being spaced closely adjacent saidsecondi'coil so that it is affected to a minor degree alsoby heat radiated therefrom, and

switching means actuated by said bimetallic 'member for controlling the energization of said econd coil, the efl'ect of said radiated heat upon said bimetallic member being to cause deenergization of said second coil by said switching means when the temperature of the second vessel is below that which it subsequently reaches due to the thermal lag of said second coil.

4. In a heat motor: a first vessel havinga movable wall, a second vessel in communication with said first vessel and forming therewith a closed system, a volatile fluid in said system, said second vessel being of elongated form and constructed of metal having good heat conductivity, said second vessel being so mounted that its major axis is substantially vertical, a first electrical heating coil surrounding a lower portion of said second vessel, a second electrical heating coil surrounding an upper portion of the second vessel, a bimetallic member mounted by one of its end portions on a still higher portion of the second vessel and in good heat-conducting relation thereto, the other end portion of the bimetallic member being spaced closely adjacent said second coil 50 that it is also subjected to a minor degree to heat radiated therefromand to heat conducted by convection from both of said coils, and switching means actuated by said bimetallic member for controlling the energization of said second coil, the effect of said radiated and convected heat upon said bimetallic member being to cause deenergization of said second coil by said switching means when the temperature of the second vessel is below that which it subsequently reaches due to the thermal lag of said second coil.

5. In a heat motor: a first vessel having a movable wall, a second vessel in communication with said first vessel and forming therewith a closed system, a volatile fluid in said system, said second vessel being of elongated formand constructed of metal having good heat conductivity, said second vessel being so mounted that its major axis is substantially vertical, 9. first and a second electrical heating coil surrounding respectively a lower and an upper portion of the side wall of said second vessel, a bimetallic member mounted by one of its end portions on the to w ll of said second vessel and in good heat-conducting relation thereto, the other end portion of the bimetallic member extending g e ally laterally closely adjacent said second coil so that i affected to a minor degree by heat radiated therea from and by heat conducted by, convection from both of said coils, and switching means actuated by said bimetallic member. for controlling the.

energization of said second coil, the effect upon said bimetallic member of said radiated and convected heat being to cause deenergization of said second heating coil by said switching means when the temperature of the second vessel is below that which it subsequently reaches due to the thermal lag or said second heating coil.

WILLIAM A. RAY. 

